1. Field
Embodiments of the inventive concept relate to a semiconductor memory device, more particularly, to a semiconductor memory device configured to apply a temperature-compensated word line voltage to a word line during a data read operation.
2. Description of the Related Art
A variation in a threshold voltage Vth of a flash memory cell may occur due to a variation in temperature.
Accordingly, during a verification read operation or a normal read operation, a temperature-compensated read voltage is applied to a selected word line to compensate for the variation in the threshold voltage relative to the temperature to obtain data information stored in a memory cell.
When a temperature compensation operation is not performed, error bits may increase, causing failures.
FIG. 1 is a diagram for explaining a variation in a threshold voltage of a memory cell according to a variation in temperature in a typical semiconductor memory device.
Memory cells connected to an arbitrary word line WLa may include programmed memory cells. The programmed memory cells may have threshold voltages, which are characterized by a threshold voltage distribution denoted by a solid curve L1, at a default temperature. In this case, the threshold voltages of the memory cells characterized by the threshold voltage distribution L1 may be determined by a read voltage V1 during a normal read operation, and by a verification read voltage V2 during a verification read operation.
The threshold voltage distribution L1 may be changed into a threshold voltage distribution denoted by a dotted curve L2, due to a variation in temperature from the default temperature. In this case, threshold voltages of memory cells characterized by the threshold voltage distribution L2 may be determined by a temperature-compensated read voltage V1′ during a normal read operation, and by a temperature-compensated verification read voltage V2′ during a verification read operation.